I used to work in a magazine warehouse that allowed us to have 1 copy of every magazine free, one of the magazines we stocked was Fortean Times so my favourite conspiracy theories are too numerous to count.
I take virtually all of these with a healthy dose of "yeah, right" so i'm not a nut but it is fun to think what if?
1: The British royal family are really space lizards (this one cracks me up)
2: Aliens had a base on the moon, this was "proved" by photos of a bridge across a crater & a spire & once these were spotted the aliens dismantled their base to prevent further detection.
3: Aliens were sighted on the first moon landing watching Neil Armstrong & buzz Aldrin from the ridge of a crater, this is apparently why there was a break in the transmission, to prevent the world from knowing the truth.
4: The faces on Mars were erased from photos by NASA to keep the secret that intelligent life once existed on Mars, another theory is that the faces were obliterated by nukes!
5: Chupacabra is an American research project that went wrong & escaped, another theory is that it is an aliens pet that escaped.
6: The world will end next year just because some lazy Mayan couldn't be bothered to make the calander go further than 2012.
7: Dinosaurs still exist in some remote rainforests, i'd love this to be true, it would explain the Chinese belief in dragons & would prove a plausable theory as to what St George fought to make himself so famous.
As much as i'd love this to be true (who wouldn't want to see real live dinosaur?) I think the only living fossils we will ever find are in the sea, one was found a few years ago after all, this is true & not conspiracy theory, it was a kind of fish thought missing from the fossil record for millions of years.
So there you go, i've only touched the tip of the iceberg for conspiracy theories that get my imagination fired up & they are in no particular order